The goal of this study is to assess long-term adjustment associated with after-school program participation for children from a disadvantaged, urban area in the northeastern United States. The developmental perspective guiding this research assumes that childhood adjustment problems are regulated by a network of biological, psychosocial, and environmental factors. Conditions of social and economic disadvantage present special constraints on the developmental process and increase the risk for long-term school failure, social behavior problems, and poor physical health. High quality, multicomponent after-school programs offer unique academic, social, and health-related opportunities that may reorganize the developmental trajectories of at-risk, disadvantaged children toward more favorable outcomes. A 4-year longitudinal investigation of after-school program participation is proposed. The research sample involves approximately 640 children in grades 1 to 3 from six public schools. Approximately 95 percent of the sample is eligible to receive free/reduced lunch and 45 percent live in poverty. The racial/ethnic characteristics are as follows: Hispanic (42.6 percent), African-American (42.3 percent), White (11.8 percent), Asian/Pacific Islander (2.9 percent), and Native American (.5 percent). The design of the study assigns students that apply to participate in after-school programs into either a target group or a control group waiting list. The after-school programs' contexts and curricula are substantially similar and include physical recreation, academic enrichment, and physical health and nutrition components. Consistent with the holistic, developmental perspective guiding the research, target and control groups will be compared on long-term academic performance, psychosocial adjustment, and physical health. Within group individual differences in adjustment will also be assessed. Results of this study will inform the knowledge base on risk and protective factors in ethnically diverse, disadvantaged populations, elucidate the link between in-school competence and beyond-the-classroom activities, and clarify the conditions under which after-school programs can serve a preventive role in the development of social-academic problems and poor physical health. This information will help to guide policy decisions at the local and national level concerning how best to design after-school programs for children in disadvantaged, urban areas of the United States.